The present invention relates to the field of integrated wheel hubs that combine hydraulic rotational power units with mechanical gear drive components such as planetary gear set reducers. More particularly, the invention relates to a novel compact arrangement of a hydrostatic rotational power unit within an integrated wheel hub.
The conventional approach to construction of integrated wheel hubs has been to locate the swashplate of the hydrostatic rotational power unit or axial piston unit deep within a large cavity formed in the stationary spindle. The spindle in turn is deeply buried in and rotatably supports the rotating wheel hub of the integrated wheel hub with the aid of appropriate bearings located between the inside of the wheel hub and the outside of the spindle. The cylinder block and piston assemblies of the hydrostatic unit reside in the cavity between the swashplate and the main opening of the cavity. A separate end cap portion with appropriate high-pressure ports therein for the hydrostatic unit then bolts to the assembly in covering relation to the rear of the cylinder block and the spindle cavity.
While this conventional arrangement provides compactness in a longitudinal or axial direction, it is not particularly compact radially. The surrounding spindle, wheel hub, and bearing structure must be quite large to accommodate the rather bulky swashplate portion of the hydrostatic unit. Furthermore, in some applications where a variable displacement hydrostatic motor would be useful, there is not enough space within the inner diameter of the spindle bearing to position and assemble the swashplate and servo system of the variable displacement hydrostatic unit. There is a need for an integrated wheel hub that is both radially and axially compact, yet able to accommodate a variable displacement hydrostatic unit.
Therefore, a primary objective of the present invention is provision of an improved integrated wheel hub assembly.
A further objective of the present invention is the provision of an axial piston unit for an integrated wheel hub.
A further objective of the present invention is the provision of an improved integrated wheel hub spindle assembly that includes therewithin a hydrostatic rotational power unit.
A further objective of the present invention is the provision of an improved integrated wheel hub spindle that includes high-pressure passageways therein for a hydrostatic unit.
A further objective of the present invention is the provision of an integrated wheel hub assembly that includes few components and utilizes a single main axle shaft.
A further objective of the present invention is the provision of an integrated wheel hub assembly that is easy to assemble and service.
A further objective of the present invention is the provision of a radially compact integrated wheel hub assembly.
A further objective of the present invention is the provision of an integrated wheel hub assembly that is economical to produce, durable, and reliable in use.
These and other objectives will be apparent from the drawings, as well as from the description and claims that follow.
The present invention relates to the field of integrated wheel hub assemblies that combine a hydrostatic rotational power unit with a wheel hub and planetary gear set. The present invention provides unique spindle and cover members that allow the hydrostatic unit to be oriented in a novel compact way within an integrated wheel hub assembly.
The integrated wheel hub assembly of this invention includes a spindle with high-pressure passages and a cavity therein that houses the cylinder block of a hydrostatic rotational power unit, a wheel hub rotatably mounted on the spindle, and an axle shaft extending through the spindle for transmitting power from the hydrostatic rotational power unit to the wheel hub through a planetary gear set reducer. The swashplate of the hydrostatic rotational power unit, which is typically the bulkiest portion of the hydrostatic unit, resides outside the confines of the wheel hub and the bearings that support the wheel hub on the spindle. This allows the spindle, wheel hub and bearings to be much smaller in diameter, which represents a considerable cost savings. The spindle with high-pressure passageways therein eliminates the need for a separate end cap.